Oh snap. Someone installed an aftermarket cruise control.
What does your dash look like? Is there a button or switch thats been added for speed control?
If you dont want or need it, you could just remove it altogether. Its aftermarket and not required to go with your swap. Otherwise leave it and i believe the SR has a second pulley on the throttle for ascd. (Automatic speed control device or the oem cruise control)
It works by adjusting your throttle position to keep you at a given speed.
Could be tapping into the harness either for speedo input to its controller or neutral safety switch to tell if the car was shifted out of gear (is it a manual or auto? Mostly likely tapping in for speedo signal i'd wager)